A Comparative Study on Two Ru^II Complexes with Thiophene‐Based Ancillary Ligands for High‐Efficiency Dye‐Sensitized Solar Cells

Abstract

Heteroleptic polypyridyl Ru complexes MMR‐1 and MMR‐2 containing 2‐(methylthio)thienyl and 2‐(4‐methoxyphenyl)thienyl units on the antennas of ancillary ligands, respectively, were designed, synthesized, and characterized as sensitizers for dye‐sensitized solar cells. The maximum absorption wavelength of MMR‐1 is more red‐shifted than that of MMR‐2, but MMR‐2 has a higher molar extinction coefficient, leading to better light harvesting. Under the same device‐fabrication conditions, the photovoltaic performances of these sensitizers were evaluated while anchored on mesoporous TiO2 and compared to that of the benchmark N719. Both MMR‐1 and MMR‐2 exhibited comparable or even higher solar‐to‐electric conversion efficiencies η with respect to N719 when employed as photosensitizers in DSSCs. Compared to MMR‐1, MMR‐2 exhibited better overall conversion efficiency, which was attributed to the electron‐donating effect of the 4‐methoxyphenyl group and the better absorptivity by harvesting higher‐energy photons. Complex MMR‐2 also showed higher open‐circuit voltage VOC than MMR‐1, which is likely due to the extension of the antenna of the ancillary ligand by inserting a phenyl group, which leads to less dye aggregation. The photovoltaic performance of MMR‐2 was better, with a short‐circuit photocurrent density of 16.76 mA cm–2, a VOC of 0.673 V, a fill factor of 73.5 %, and an η value of 8.29 % with the addition of 0.5 m 4‐tert‐butylpyridine (TBP) compared to 8.18 % for N719.

N719 Derivatives for Application in a Dye-Sensitized Solar Cell (DSSC): A Theoretical Study

“…In general, the following dye sensitizers are employed in DSSCs (maximum efficiency obtained is shown in parenthesis): metal–organic complexes (11%), metal-free organic dyes (10%), porphyrin dyes (12% in a co-sensitized processes), quantum-dot sensitizer (7.4%), and perovskite-based sensitizer (25%). − Regarding metal–organic complexes, most of the investigations are focused on the ruthenium complexes dyes (RuL 2 (NCS) 2 ) ( L = 2,2′-bipyridyl-4,4′-dicarboxylic acid) and its tetrabutylammonium salt, named as N3 and N719, respectively. − In the case of the best performing DSSC reported before, a thin layer of nanocrystalline TiO 2 film was sensitized with ruthenium complex due to highly stable performance compared with that of other sensitizers.…”

Highly Efficient Rigidified Quinoxaline‐based Co‐Sensitizers Carrying Long Alkyl Chains for Ruthenium‐Complex‐Sensitized DSSCs**

“…Iodolyte (Solaronix, HI‐30) was chosen as the electrolyte and the illumination condition was set as AM 1.5. In addition, co‐adsorbent CDCA can effectively decrease the undesirable charge recombination occurring in the interface of Pt/electrolyte and FTO/TiO 2 /dye in DSSCs [43–45] . Herein, HD ‐ 2 and LY01 ‐ LY03 were adsorbed on the surface of TiO 2 with the presence of 20 m m CDCA for fabricating cosensitized cells.…”

Molecular engineering of ruthenium-based photosensitizers with superior photovoltaic performance in DSSCs: novel N-alkyl 2-phenylindole-based ancillary ligands

“…21–24 Previously in our group, the construction of ancillary ligands to obtain a near-infrared region absorption response has been the main research theme for several years and many striking Ru( ii ) sensitizers have been synthesized and fabricated. 25–31…”